Study On The Metallic Catalysts Used For Pet Synthesis

A series of metal ethylene glycol compounds has been made by ourselves which were used for PET synthesis.The acetates of the same metal were also used for comparison.The effect of these metal compounds on catalyzing esterification and polycondensation and on the properties of the obtained PET have been researched.In this thesis the complex stability constant expression about coordination bond energy was firstly direct connected with intrinsic viscosity or molecular weight of PET.Based on,a new and better expression has been raised.The kind of metal elements used for PET synthesis could be chosen by calculation with this new expression.The experiments have shown that all the selected metal compounds could catalyze the esterification and polycondensation.But the degree of the effect was different: for the same anion the different metal elements catalyzing different;for different anion the same metal element catalyzing different.For a same metal compound the catalyzing effect was different from esterification to polycondensation.All the experimental results have proves that the titanium compound was the most catalytic active,and for a same metal the ethylene glycol compound was better than that of acetate.The thermal performance of PET synthesized with different metal compound was tested by DSC and TG.It turned out that PET catalyzed by Fe、Zn、Ca、Co compound has better thermostability,while PET catalyzed by Ti、La、Sb compound has poor thermostability.PET catalyzed by Mn、Ca、Pb、Co compound has higher transition temperature,while catalyzed by Zr and Sb has lower transition temperature.For a same metal the PET catalyzed by ethylene compound has better thermostability.The crystallization rate of PET synthesized with different metal compound was also measured.The results showed that for different metal compound the obtained PET has different crystallization velocity and different crystallization temperature range.The results of the crystallization velocity of PET catalyzed by different metal was: La﹥Mg﹥Zr﹥Al﹥Ca﹥Pb﹥Fe﹥Co﹥Sb﹥Zn﹥Ti.